Atherectomy apparatus with imaging

ABSTRACT

The present invention relates to apparatuses for cutting and removing occlusive material with imaging capabilities. According to certain aspects, the apparatus includes a catheter body, a rotatable shaft, and an imaging element. The catheter body defines a lumen and includes a distal housing that defines an opening. The rotatable shaft is disposed within the lumen of the catheter body. The rotatable shaft includes a conveying component and a cutting element that is at least partially surrounded by the distal housing. The imaging element is located on the distal housing of the catheter body.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/118,585, filed Feb. 20, 2015, thecontents of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This application relates to the treatment of occluded body lumens,including the removal of occlusive material from a blood vessel.

BACKGROUND

Thrombosis is a medical condition that results from the formation of ablood clot, or thrombus, within a vessel. Deep vein thrombi oftendevelop in the veins of legs or lower abdomen, but thrombi may occur inother vessels. The clot is typically formed from a pooling of bloodwithin a vein due to abnormally long periods of rest, e.g. when anindividual is bed ridden following surgery or suffering a debilitatingillness. In addition to thrombosis, atherosclerosis is another medicalcondition that results from the formation of a blockage in a vein.Atherosclerosis is due to the build of atheroma material along thearterial walls. Atheroma deposits can have widely varying properties,with some deposits being relatively soft and others being fibrous and/orcalcified. In the latter case, the deposits are frequently referred toas plaque. Often thrombosis and atherosclerosis are both present in theveins. For example, a thrombus develops around the atheroscleroticplaque.

The formation of thrombi and build-up of plaque can lead to stroke orembolism, which may cause serious health issues, including death.Strokes occur when the blood clot or plaque blocks an artery supplyingblood to the brain, thus depriving brain tissue of oxygen. Withoutoxygen, brain cells begin to die. Embolisms occur when a blood clottravels around the body and lodges itself in an organ. For example, apulmonary embolism is a blockage of the blood supply to the lungs thatcauses severe hypoxia and cardiac failure.

For some blockages, surgical intervention may be necessary to remove thethrombus, plaque, or both from a vessel, such as when cholesterol oranti-coagulant medications are not able to reduce the blockage. Balloonangioplasty is a common surgical treatment, and involves placing aballoon within the occlusion and inflating the balloon to macerateand/or displace plaque and other clots against the vessel wall. Whilegenerally effective, balloon angioplasty can undesirably stretch theartery, rip the vessel wall, and induce scar tissue formation, which maylead to restenosis of the artery. Atherectomy is another form oftreating occluded vessels, and involves the use of an intravasculardevice to mechanically remove (e.g., de-bulk) blockages (e.g. plaque,thrombi, etc.) from the wall of the artery. While atherectomy devicesare able to remove clots without stretching or ripping, there are somedrawbacks. Atherectomy devices are often unable to remove the resultingmorcellated plaque particles, and the generation of such particlessignificantly reduces angiogram visualization during the procedure.

SUMMARY

The present invention provides devices and methods for the mechanicalbreakdown and removal of blockages (e.g., plaque, thrombi, etc.), whichsimultaneously allow intraluminal imaging of the treatment site andprocedure. Particular advantages of the invention include pre-treatmentvisualization of the type and severity of the occlusion, real-timeintraluminal assessment of the mechanical breakdown of the occlusion formore complete and safe dissolution, and elimination of the exchange ofmultiple devices (e.g. need for a separate imaging catheter). Devices ofthe invention are well-suited to remove plaque and other atheromadeposits, but may also be used to treat thrombosis.

Devices of the invention generally include a catheter body and arotatable shaft disposed within the catheter body. The rotatable shaftincludes a cutting member coupled thereto and a conveying element alongthe length of the rotatable shaft. The distal end of the catheter bodyincludes a housing that defines a distal opening and at least partiallysurrounds the cutting member. An imaging element is located on thehousing and allows one to locate and assess the occlusion within avessel, observe cutting and removal of the occlusion, and assess thevessel after treatment. For treatment, the cutting member rotates tomechanically breakdown the blockage, and the resultant blockageparticles are driven from the vessel and into the catheter body via theconveying component.

The imaging assembly of the apparatus advantageously providesintraluminal guidance during treatment. The imaging assembly may be aforward-viewing imaging element, a side-viewing imaging element, or acombination thereof. Suitable imaging assemblies include ultrasoundimaging assemblies and optical coherence tomography imaging assemblies.

In addition to imaging both vessels, the obtained image data can besubject to data processing (e.g., spectral analysis) such that blockagecan be characterized. Processing techniques for characterizing objectspresent in the image data may include, for example, determining thedensity of the occlusion, determining the composition of the occlusion,determining a blood-tissue border of the lumen of the one or morevessels.

Generally, apparatuses of the invention include one cutting element,although some embodiments include more than one cutting element. Thecutting element may include one or more flutes that form a cuttingblade. The flutes typically have a positive rake angle. The positiverake angle may be at least 20 degrees. In some variations, the positiverake angle may range from 40 to 80 degrees. The cutting element may alsoinclude one or more crushing elements. The crushing elements may have anegative rake angle and are substantially rectangular in shape. Thenegative rake angle may range from at least 1, 5, 10, 15, 20, 25, 30degrees or more. Where the cutting element is designed to slice/cutthrough the blockage, the crushing element is configured to provideblunt force to the blockage. It is contemplated that other positive andnegative rake angles may be use for the cutting element and the crushingelement.

Apparatuses of the invention include a conveying element associated withthe rotatable shaft. The conveying element acts to remove the brokendown particles from the vessel, thereby minimizing the amount ofparticles that are undesirably released into the blood stream. Accordingto certain embodiments, the conveying element is a helical wire woundabout the rotatable shaft, similar to a screw. When rotated, theconveying element drives particles proximally down the inner lumen ofthe catheter body. The particles may be deposited in a storageassociated with the catheter body. The cross-section of the conveyingelement may be circular or rectangular. A rectangular cross-sectionincreases the contact between the conveying element and an inner luminalsurface of the catheter body, thereby increasing the conveying elementsability to drive particles within proximally within the catheter body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows anatomic views of segments of an artery, cut in section, toillustrate different degrees of atherosclerosis.

FIG. 2 depicts a diagrammatic anatomic view showing the major arteriesof a right leg and typical variations in diameter of the variousarteries.

FIG. 3A depicts a perspective view of an illustrative variation of anatherectomy system as described here.

FIG. 3B shows an enlarged perspective view of a distal portion of theatherectomy system shown in FIG. 3A.

FIGS. 4A-4D depict illustrative methods by which an atherectomy systemmay be deployed intravascularly.

FIG. 5A depicts an exploded perspective view of a variation of theatherectomy systems described here.

FIG. 5B depicts an assembled cross-sectional side view of theatherectomy system of FIG. 5A.

FIGS. 6A and 6B depict a perspective distal view and a side view,respectively, of a variation of a representative cutting element asdescribed here.

FIG. 6C is a cross-sectional view of the representative cutting elementtaken along line 8C-8C in FIG. 6B.

FIG. 6D is a cross-sectional view of the representative cutting element,like that shown in FIG. 6C, cutting into occlusive materials.

FIG. 7 depicts a distal perspective view of a variation of a cuttercomprising first and second cutting elements.

FIGS. 8A-8C depict various views of a cutting element, according tocertain embodiments.

FIGS. 9A-9B illustrates cross-sections of the internal conveying member,according to certain embodiments.

FIG. 10 illustrates removal of occlusion through atherectomy devicesdescribe herein.

FIG. 11A depicts a perspective view of a variation of the atherectomysystems described here.

FIG. 11B is an enlarged perspective view of a distal portion of theatherectomy system shown in FIG. 11A.

FIGS. 11C and 11D depict different manners in which the atherectomysystem as shown in FIG. 11A may be manipulated.

FIG. 12A is an exploded perspective view of a variation of theatherectomy systems described here.

FIG. 12B depicts an assembled cross-sectional side view of theatherectomy system shown in FIG. 12A.

FIG. 13A is an exploded perspective view of a portion of the atherectomysystem of FIGS. 12A and 12B.

FIG. 13B depicts an assembled perspective view of the componentsdepicted in FIG. 13A.

FIGS. 13C and 13D depict a manner in which the atherectomy system shownin FIGS. 12A and 12B may be manipulated.

FIGS. 14A-14E and FIGS. 14F(1)-14F(5) depict a manner by which theatherectomy apparatus (2000) described above in relation to FIGS. 12Aand 12B may be actively and passively steered within a vessel.

FIGS. 15A and 15B depict a variation of the atherectomy apparatusesdescribed here.

FIG. 16 illustrates a system for uses with atherectomy apparatusesdescribed herein.

DETAILED DESCRIPTION

The present invention provides atherectomy devices for removingocclusions within blood vessel while allowing real-time imaging of theprocedure.

In certain embodiments, the devices and methods of the present inventionare designed to break down and remove blood clots, such as such asemboli and thrombi, atheroma, plaque and other occlusive material frombody lumens. The body lumens generally are diseased body lumens and inparticular coronary arteries. The defect in the body lumen can be a denovo clot or an in-stent clot for example. The devices and methods,however, are also suitable for treating stenosis of body lumens andother hyperplastic and neoplastic conditions in other body lumens, suchas the ureter, the biliary duct, respiratory passages, the pancreaticduct, the lymphatic duct, and the like. Neoplastic cell growth willoften occur as a result of a tumor surrounding and intruding into a bodylumen. Removal of such material can thus be beneficial to maintainpatency of the body lumen. The devices and methods of the presentinvention can collect lumenectomy samples or materials. While theremaining discussion is directed at aspirating, imaging, and passingthrough atheromatous or thrombotic occlusive material in a coronaryartery, it will be appreciated that the systems, devices, and methods ofthe present invention can be used to aspirate and/or pass through avariety of occlusive, stenotic, or hyperplastic material in a variety ofbody lumens.

Atherectomy devices of the invention are particularly well-suited forthe treatment of atherosclerosis. Atherosclerosis commonly affects themedium and large arteries, and may occur when fat, cholesterol, andother substances build up on the walls of arteries and form fleshy orhard/calcified structures called plaques/lesions. FIG. 1 shows aninstance of a first normal arterial segment (100) having a nativearterial wall (102), a second arterial segment (104) with mildatherosclerosis and initial plaque (106) formation on the nativearterial wall (108), and a third arterial segment (110) with severeatherosclerosis and having advanced plaque (112) formation on the nativearterial wall (114). As plaque forms within the native arterial wall,the artery may narrow and become less flexible, which may make it moredifficult for blood to flow therethrough. In the peripheral arteries,the plaque is typically not localized, but can extend in length alongthe axis of the artery for as much as 10 mm or more (in some instance upto 400 mm or more).

One of the clinical challenges of atherectomy arises from the nativeanatomy of certain peripheral regions where atherectomy is indicated(for example, in the leg). Accordingly, the following is a descriptiveof the leg anatomy for perspective of certain uses of atherectomydevices of the invention. FIG. 2 shows the anatomy of major arteries ofa leg (200) (the right leg is shown for the purpose of illustration).Also shown there is the abdominal aorta (202), the left iliac artery(204), the right iliac artery (206), the internal iliac artery (208),the external iliac artery (209), the common femoral artery (210), thesuperficial femoral artery (212), the popliteal artery (214), thetibioperoneal trunk (216), the posterior tibial artery (218), theanterior tibial artery (220), and the peroneal artery (222). Thediameters of the peripheral arteries of the leg generally taper fromlarger to smaller in the direction of arterial blood flow from above theknee to below the knee.

The abdominal aorta (202) is the largest artery in the body, and itsdiameter can range from 19 to 25 mm (about 0.75 to about 1 inch). Theabdominal aorta successively branches or divides numerous times betweenthe proximal and distal regions of the legs. Each successive branch ordivision may reduce the diameter of the arteries in the direction ofarterial blood flow from the heart to the feet, and the tortuousity ofthe path generally increases.

The first branching is at the groin, into the left (204) and right (206)common iliac arteries. In the left leg, the left common iliac artery(204) branches into the internal (208) and external (209) iliacarteries. Near the head of the femur bone (224), the external iliacartery (209) becomes the common femoral artery (210) or “CFA”. The CFAfurther connects to the superficial femoral artery (212) or “SFA”. TheSFA connects to the popliteal artery (214), which runs behind theflexible region of the knee. Above the knee, the SFA generally has adiameter of about 5 to 7 mm, or about 0.2 to 0.25 inch. Traversingdistally below the knee (toward the feet), the popliteal artery (214)may further reduce in diameter to about 4 to 4.5 mm (0.157 inch to 0.177inch), and then further to about 3.5 mm (0.137 inch). Traversing furtherdistally, the popliteal artery (214) eventually branches again into theanterior tibial artery (220) and the tibioperoneal trunk (216),resulting in a further reduction in diameter to about 3.0 mm to 2.5 mm(0.118 inch to 0.098 inch). Traversing further distally, thetibioperoneal trunk further subdivides into the posterior tibial (218)and peroneal (222) arteries, further reducing diameter to about 2.0 mm(0.078 inch). Overall, the diameters of the peripheral arteries of theleg vary typically from about 2 mm (below the knee) to about 7 mm (abovethe knee).

Atherectomy devices are usually introduced into the vasculature thoughan iliac artery by either an ipsilateral (i.e., same side) or acontralateral (i.e., opposite side) approach, and typically advancedunder fluoroscopic radiographic image guidance through the CFA and intothe SFA. Currently, nearly all intravascular atherectomy cases areperformed in the SFA, however, in a majority of these cases, potentiallytreatable atherosclerosis exists on multiple levels of the peripheralarteries, both above and below the knee. Accordingly, the devices andmethods described here may be helpful in reaching these potentialatherectomy sites.

FIGS. 3A and 3B illustrate an atherectomy system of the invention,according to certain embodiments. As shown there, the atherectomy system(300) may include an intravascular atherectomy apparatus (302) and aguide wire (304) over which the atherectomy apparatus (302) may bedeployed. The guide wire (304) is preferably silicon-coated ornon-coated (bare), or otherwise free of a PTFE coating. It should beappreciated, however, that in some variations the atherectomy systemsdescribed here may comprise a guide wire that includes a PTFE coating,or that does not include a guide wire at all. In certain embodiments,the guidewire may be a sensing guidewire. For example, the guidewire maybe configured to measure functional parameters, such as flow, pressure,temperature, etc. Exemplary functional measurement devices suitable foruse in practicing the invention include FloWire Doppler Guidewire andthe ComboWire XT Guidewire by Volcano Corporation.

The atherectomy apparatus (302) generally includes an elongated catheterbody (306) having a central axis. The catheter body (306) may be sizedand configured to be advanced over the guide wire (304) in a bloodvessel from an external percutaneous access site. The access approachcan be ipsilateral or contralateral, and down to the targeted region.For example, FIGS. 4A and 4B depict views of the anatomy of a patientwith a distal portion of the atherectomy apparatus (302) advanced usingan ipsilateral approach to a target region in the anterior tibial artery(220). As shown there, the atherectomy apparatus (302) may be introducedinto an access site (400) in the right iliac artery (400). Conversely,FIGS. 4C and 4D depict views of the anatomy of a patient with a distalportion of the atherectomy apparatus (302) advanced in a contralateralapproach. As shown there, a distal portion of the atherectomy apparatus(302) may be advanced through an access site (404) in the left iliacartery (204), across the iliac bifurcation, and down to the targetedsite (in these figures, the targeted site is shown as a branch of theprofunda artery (406). In order to follow the intravascular path fromthe access site to the target region, the catheter body (306) shouldpossess physical and mechanical properties to allow the catheter body(306) to follow the guide wire through a bending, often tortuousintravascular path, as will be described in more detail below.

The atherectomy apparatus (302) may also include a handle (308) iscoupled to the proximal (i.e., closest to the caregiver) end of thecatheter body (306). The handle may be sized and configured to besecurely held and manipulated by a caregiver outside an intravascularpath. The handle may be manipulated from outside the intravascular pathnear the percutaneous access site, which may allow a caregiver toadvance the catheter body through the intravascular path, which, in theleg, generally becomes more tortuous as one proceeds toward the distalregions of the legs (below the knee and toward the feet). Image guidance(e.g., CT, radiographic, in situ visualization carried on board theatherectomy apparatus or otherwise provided, or another suitableguidance modality, or combinations thereof) may be used to aid inadvancement or positioning of the atherectomy apparatus (302). Thecatheter body (306) may be advanced to provide access to a targetedregion where fat, cholesterol, and other substances have accumulated onthe walls of arteries to form plaques or lesions, which will also ingeneral be referred to as “occlusive materials.”

The atherectomy apparatus (302) may further comprise a cutter assembly(310) at the distal end (e.g. farthest from the handle) end of thecatheter body. Generally, the cutter assembly may act to cut and capturethe occlusive material, and thereby remove occlusive material from theartery, which may open the artery to blood flow. In some variations, thecutter assembly (310) may include a rotatable cutter (312) at leastpartially housed within a concentric cutter housing (314). The cutter(312) may be rotatable within the housing around the central axis of thecatheter body. In the variation shown in FIGS. 3A and 3B, the cutterhousing (314) may be open at its distal-most end such that thedistal-most end of the cutter may project a distance distally from theopen housing (314). In some of these variations, when the cutterassembly (310) is deployed in the targeted region where the occlusivematerials exist, there may be no structure or component of theatherectomy located in front of (i.e., distal to) the cutter assembly,and thus the first region of the atherectomy apparatus to interact withthe plaque is the cutter assembly.

The cutter housing (314) may include an imaging assembly (311) locatedthereon or embedded therein. The imaging assembly (311) may be used toobtain real-time images of the occlusion (atheroma, plaque, thrombi, oremboli) prior to morcellation with the cutter (312), duringmorcellation, and after morcellation to observe completeness of theprocedure or whether more cutting is necessary to remove the blockageentirely or regain a suitable luminal opening. Suitable imagingassemblies include optical-acoustic imaging apparatus, intravascularultrasound (IVUS), forward-looking intravascular ultrasound (FLIVUS) oroptical coherence tomography (OCT). Preferably, the imaging assembly(311) is an ultrasound-based imaging assembly. The ultrasound imagingassembly may be a phased-array assembly, which includes a plurality oftransducer elements. The imaging assembly (311) may located/embedded ona portion of the housing (314). In certain embodiments, the imagingassembly (311) circumscribes the housing (314). In other embodiments,the imaging assembly (311) is located on the catheter body (306)proximal to the housing (314). Imaging assemblies, such as imagingassembly (311), are described in more detail hereinafter.

FIGS. 5A and 5B show a breakdown of an atherectomy apparatus (500)suitable for use with the atherectomy systems described here. As shownthere, atherectomy apparatus (500) may comprise a handle (502), acatheter body (504), and a cutter assembly (506), such as describedabove with respect to FIGS. 3A and 3B. As shown in FIGS. 5A and 5B, thecutter assembly (506) may comprise a ferrule (508), a cutter housing(510), and a cutter including a first cutting element (512) and a secondcutting element (514). It should be appreciated that the atherectomyapparatus (500) may comprise any suitable cutter assembly, such as thosedescribed in more detail below. The housing 510 may include an imagingassembly 511. The imaging assembly 510 is connected to one or moresignal wires (513), which are in turn connected to a signal processingapparatus. The signal wires (513) transmit energy to the imagingassembly 511 to emit imaging signals (such as ultrasound or opticalsignals) and transmit back signals (back-echos) received from theimaging assembly to a signal processing apparatus and imaging console.The signal wires (513) may run alongside an inner surface of thecatheter body (504) to the signal processing apparatus, or the signalwires (513) may be incorporated into the catheter body (504). In certainembodiments, the catheter body (504) may define a separate lumen throughwhich the signal wires (513) may be routed.

The atherectomy apparatus (500) may include a motor (516), which in theembodiment shown in FIGS. 5A and 5B, may be contained within a housingportion (518) of the handle (502). The motor is desirably batteryoperated, either by use of replaceable batteries, by use of rechargeablebatteries, or combinations thereof. A motor controller may desirablyprovide a consistent supply of power through all operating conditions,including no load through excessive torque and stall conditions. Acontrol switch (520) (e.g., slide switch, pushbutton, and/orpotentiometer) may be provided to include an off/on function, and insome instances, one or more of a variety of other control functions,such as ramp up and/or ramp down, and/or variable speed. In somevariations, the motor may run at about 12,000 RPM at 6 volts nominal.The operating parameters can be changed by adjusting the gear ratio.

As shown in FIGS. 5A and 5B, a torque shaft (522) may connect the motor(502) to the cutter. Specifically, the motor (502) may rotate the torqueshaft (522), which may in turn rotate the cutter within the cutterhousing (510) around the central axis of the catheter body. Rotation ofthe cutter of the cutter assembly (506) may cause the first (512) and/orsecond (514) cutting elements to cut occlusive material and convey theocclusive materials into the cutter housing (510) (a process also knownas “debulking”). Preferably, the cutter assembly (506) captures the cutocclusive materials from the blood without the use of any vacuumaspiration (although it should be appreciated that in some variations,vacuum aspiration may assist conveyance of the cut occlusive material).

Additionally, the atherectomy apparatus (500) may further include aninternal conveyor (524) on the torque shaft (522). As occlusive materialis conveyed into the cutter housing (510) by the cutter, the conveyor(524) may convey the cut occlusive material further back (proximally)along the catheter body for discharge outside the patient's body. Asmentioned above, this conveyance may occur without the use of vacuumaspiration assistance. Mechanical conveyance may complement distalcapture. Because it does not require the assistance of vacuumaspiration, mechanical conveyance may minimize the risk of the arterycollapsing around the cutter and the associated risk of perforation.Additionally, this conveyance may maximize the removal of tissue andblood components that have been damaged by contact with the cutterassembly.

In further embodiments, the catheter body (504), housing (510) coupledthereto, and imaging assembly (511) located on the housing (510) areconfigured to rotate. For example, the components may be coupled to arotary drive shaft to enable rotation. Rotary drive shafts configured toenable rotation of catheter bodies and imaging elements are known in theart. Rotation of these components may serve several purposes. Forexample, the rotation can act as a means to further dissolve theblockage. In another example, the rotation can assist in moving thebroken down blockage particles into the catheter body (504) for removal.Additionally, the rotation can serve to assist in imaging the luminalsurfaces of the vessel wall (e.g. the luminal surfaces within intramuralspace). For example, imaging elements (such as optical coherencetomography and ultrasound imaging elements) capture cross-sectionalimaging data obtained during a rotation of the imaging element. In someembodiments, the rotation of the catheter body (504) and associatedelements counters the rotation of the torque shaft (522). This counterrotation may increase effectiveness of the internal conveyer (524) inremoving the broken down particles.

The individual components of the systems shown in FIGS. 3A, 3B, 5A and5B are discussed in more detail hereinafter.

B. The Catheter Body

1. Dimensions

For practical purposes, the outer diameter of any section of thecatheter body, including the cutter assembly it carries, may be dictatedat least partially by the anatomy of the intravascular path and theintended target region. Specifically, it may be desirable to maximizethe cutting effectiveness of the cutter assembly by maximizing thediameter of the cutter, while minimizing the potential of puncture ortrauma to the vessel. Additionally, the outer diameter of the catheterbody/cutter assembly may also be dictated at least partially by thediameter of a guide sheath or introducer selected that may be placed atan access site to allow introduction of the atherectomy apparatus intothe vasculature. It may be desirable to select a guide sheath orintroducer sized to minimize pain, trauma, and blood loss during use,and to facilitate rapid closure of the access incision after removal, tothereby reduce the incidence of interventional complications.

As mentioned previously, diameters of the peripheral arteries of the legvary typically from relatively small in regions below the knee (2.0 mm)to relatively large in regions above the knee (7.0 mm). For percutaneousaccess to the peripheral arteries, clinicians typically use guidesheaths sized from 5F (diagnostic) to 7F (interventional).

Assuming, for example, that a 7 French guide sheath would likely be,from a clinical perspective, the largest selected to access the largervessels above the knee (4 mm to 7 mm), and allowing for a reasonableclearance tolerance between the catheter body/cutter assembly and theguide sheath, in some instances the outer diameter of the catheter bodyfor introduction through such a guide sheath may be selected to beapproximately equal to or less than about 2.4 mm. Assuming that a 5 Fguide sheath would likely be, from a clinical perspective, the largestused to access the smaller vessels below the knee (2.5 mm to 3 mm), andallowing for a reasonable clearance tolerance between the catheterbody/cutter assembly and the guide sheath, in some instances the outerdiameter of the catheter body for introduction through such a guidesheath may be selected to be approximately equal to or less than about1.8 mm. Assuming that an intermediate 6 French guide sheath would likelybe, from a clinical perspective, the largest used to access theintermediate vessels near the knee (3 mm to 4 mm), and allowing for areasonable clearance tolerance between the catheter body/cutter assemblyand the guide sheath, in some instances the outer diameter of thecatheter body for introduction through such a guide sheath may beselected to be approximately equal to or less than about 2.2 mm.

It may desirable that the outer diameter of the cutter assembly bemaximized, to maximize the overall cutting area of the atherectomyassembly. When the cutter assembly of an atherectomy apparatus is thedistal-most component of the apparatus, the cutter assembly may lead theway by cutting through the occlusive materials. With regard to thecatheter body, however, there may functional and clinical benefits thatarise when the outer diameter of the catheter body is not maximized tomatch the outer diameter of the cutter assembly. Reducing the diameterof the catheter body relative to the cutter assembly may minimizefrictional contact between the catheter body and the vessel wall. Thismay lessen the force required to advance the catheter body through thevasculature and occlusive material, and may help prevent the catheterbody from dragging against or sticking to tissue structures in thevessel, or otherwise impeding the progress of the cutter assemblythrough the occlusive materials.

For example, it may be desirable that the outer diameter of the catheterbody proximal of the cutter assembly be sized smaller than the outerdiameter of the cutter assembly. In other instances, it may be desirablethat the outer diameter of the catheter body proximal of the cutterassembly be sized equal to or smaller than the outer diameter of thecutter assembly. For example, in the variation of atherectomy apparatus(500) described above with respect to FIGS. 5A and 5B, the catheter body(504) may have an outer diameter less than an outer diameter of thecutter assembly (506).

The reduced diameter of the catheter body may also permit the injectionof radiographic contrast material around the catheter body in the guidesheath. For example, an atherectomy apparatus for introduction through a7F introducer system may have a 2.4 mm diameter cutter assembly and acatheter body having a 2.2 mm diameter. In other variations, anatherectomy apparatus for introduction through a 5F or 6F introducersystem may have a 1.8 mm diameter cutter assembly and a catheter bodyhaving a 1.6 mm diameter, or a 2.2 mm diameter cutter assembly and acatheter body having a 1.6 mm diameter.

2. Catheter Properties

In addition to the anatomical and clinical considerations that may beused in selecting an outer diameter of a catheter body, the catheterbody may also desirably possess certain physical and mechanicalproperties, such as those described immediately below, which may enhancethe function of the catheter body to support and guide passage of thecutter assembly through the intravascular path and the occlusivematerials.

(i) Column Stiffness (Pushability)

One potentially desirable property for the catheter body includes columnstiffness. Expressed in units of inch/foot-pounds, column stiffness isthe capability of the catheter body to withstand an axial load orcompression while resisting bending. Column stiffness can be measuredand characterized in conventional ways, and may be referred to as“pushability” herein. Generally, a higher column stiffness is desirable,and may allow the catheter body to transmit a higher axial force(compression) applied at the handle to the cutter assembly withoutbuckling. Accordingly, it may be desirable that the catheter bodypossess column stiffness sufficient to push the cutter assembly over theguide wire without buckling. A column stiffness of 0.050 inches/lbf orgreater may be desirable for the catheter bodies described here.

(ii) Tensile Stiffness (Pullability)

Another potentially desirable property for the catheter body comprisestensile stiffness. Expressed in units of inch/foot-pounds, tensilestiffness is the capability of the catheter body of withstanding tensionwhile being stretched or pulled before the cross section starts tosignificantly contract (called “necking”). Tensile stiffness can bemeasured and characterized in conventional ways, and may be referred toas “pullability” herein. Generally, a high tensile stiffness may bedesirable, and may allow the catheter body to be pulled proximally alongan intravascular path (e.g., to withdraw the cutter assembly) withoutnecking. A tensile stiffness of 0.050 inches/lbf or greater may bedesirable for the catheter bodies described here.

(iii) Torsional Stiffness (Torquability)

Another potentially desirable property for the catheter body comprisestorsional stiffness. Expressed in degrees/ounce-inch, torsionalstiffness is the capability of the catheter body to transmit arotational load (torque) without untwisting, over-twisting and/ordeforming. Torsional stiffness may be measured and characterized inconventional ways, and may be referred to as “torquability” herein. Thetorsional stiffness may control the capability of the catheter body totransmit a given amount of rotation applied at its proximal end (i.e.,the handle) to achieve a comparable amount of rotation at its distal end(i.e, the cutter assembly). A higher torsional stiffness may bedesirable, to better allow for rotational transmission along theatherectomy apparatus (i.e., around a guide wire), without twisting ordeforming. A torsional stiffness that achieves a 1:1 relationshipbetween rotation applied at the proximal end and the rotation observedat the distal end may be desirable for the catheter bodies describedhere.

(iv) Bending Stiffness (Trackability)

Another potentially desirable property for the catheter body comprisesbending stiffness. Expressed in units of a bend radius (in inches),bending stiffness is the ability of the catheter shaft to bend inresponse to an applied bending force, without breaking or deforming(i.e., without taking a set). Bending stiffness is an extensive materialproperty that can be measured and characterized in conventional ways,and may be referred to as “trackability” herein. Generally, a lowerbending stiffness may be desirable to allow the catheter body to benavigated over a guide wire around sharp bends in the vasculature. Atargeted bending stiffness of 0.5 inches (bend radius) or greater atmid-length of the catheter body may be desirable for the catheter bodiesdescribed here. If the catheter body includes an active deflectioncomponent at its distal end (as will be described in greater detaillater), a targeted bending stiffness of 1.0″ (bend radius) at thedeflectable distal end may be desirable for the catheter bodiesdescribed here. A prescribed minimum bend radius also makes it possibleto coil the catheter body for packaging without taking a set.

Conventionally, trackability is thought to be inversely related topushability/pullability and torquability. That is, greater pushability,pullability, and/or torquability in a catheter body may reduce thetrackability of the catheter body. However, the catheter bodiesdescribed here may balance the pushability, pullability, torquability,and trackability for a given catheter body. The result may be a catheterbody that is trackable, yet also possesses the requisite columnstrength, tensile strength, and torsional stiffness to be sufficientlypushable, pullable and torquable to allow navigation and advancement ofa cutter assembly.

The overall trackability of a given catheter body (in terms of itsability to reliably navigate over a guide wire) may be influenced mainlyby the physical and mechanical characteristics of the catheter body atits distal end. The pushability, pullability, and torquability may beinfluenced mainly by the physical and mechanical characteristics of thecatheter body proximal to its distal end. That is, the overallconfiguration of different regions of a catheter body may impartcharacteristics to the overall length of the catheter body, which mayallow for optimization of the overall pushability, pullability,torquability, and trackability of the catheter body.

3. Catheter Body Variations

Generally, the column stiffness, tensile stiffness, torsional stiffness,and bending stiffness for a catheter body may be at least partiallydetermined by its constituent material or materials, the dimensions ofcatheter body (e.g., the interior diameter, the outer diameter, wallthickness, etc.) and other structural features such as patterning. Thecatheter bodies may be fabricated from a metal tube (for example, a type304 stainless steel tube or the like). The dimensions of the tube maydepend at least partially on the intended use of the atherectomyapparatus. For example, in some variations the outer diameter of thetube may desirably be about 2.2 mm, while in other variations the outerdiameter of the tube may be about 1.6 mm. Additionally or alternatively,the wall thickness of the tube may preferably be about 0.288 mm.Additionally or alternatively, the overall length of the tube maypreferably be about 1437 mm (about 56.56 inches).

A metal tube with some or all of the dimensions described immediatelyabove may provide a high degree of pushability, pullability, andtorquability, the baseline bending stiffness may limit the trackabilityof the catheter body given the length of the catheter body. Accordingly,in some variations, the bending stiffness of the metal tube may beincrementally modulated along the length of the catheter body bycreating zones of cut patterns along at least a portion of the length ofthe catheter body. The cut patterns may be formed in any suitable manner(e.g., via laser cutting), and the zones may impart a desired profile ofbending stiffness over the length of the catheter body. For example, cutpattern zones may be used to incrementally decrease the bendingstiffness in a stepwise fashion from proximal end to distal end, toprovide a minimum bending stiffness conducive to trackability at thedistal end (where trackability is more desirable). The stepwise fashionin which the bending stiffness is decreased may be configured in amanner to help maintain the overall pushability, pullability, andtorquability. In certain embodiments, one or more zones of the catheterbody include helical cut patterns, threaded cut patterns, spiral cutpatterns, or brickwork cut patterns. A catheter body having any of thecut patterns can be lined or jacketed with a polymeric material, andfurther may be treated to produce hydrophilic, hydrophobic, or drugbinding (heparin, antimicrobial) properties.

4. Catheter Body Rotation

As discussed above, the catheter body 504 (along with the housing andimaging assembly) may be configured for rotation. In certainembodiments, the catheter body 504 is coupled to a rotary drive shaftthat drives the rotation of the catheter body 504. In other variations,the catheter body can be coupled to a post on the handle that is sizedand configured to rotate in response to rotation of a control knob. Forexample, the atherectomy apparatus (500) described above with respect toFIGS. 5A and 5B may comprise a rotation knob (526). Rotation of the knobmay apply torque to the catheter body to selectively rotate the cutterassembly. An indexing mechanism can be provided to provide stepwisecontrol, with tactile and/or audible feedback, so that the caregivermaintains knowledge of the rotational position of the cutter assemblywithout taking their eye off the radiographic or otherwise providedin-situ image.

It is also possible to apply torque to the catheter body by rotating thehandle itself. Selective rotation of the cutter assembly can thus befinely controlled by a combination of control knob manipulation andhandle twisting.

C. The Cutter Assembly

As mentioned above, the atherectomy device may comprise a cutterassembly. The cutter assembly may comprise a ferrule, a cutter housing,and a cutter comprising at least one cutter element. In variations inwhich the cutter assembly comprises a ferrule, the cutter assembly maybe joined to the distal end of the catheter body by the ferrule. Incertain embodiments, the cutter assembly further includes an imagingassembly associated with the cutter housing.

1. The Cutter Housing

As mentioned previously, the cutter assembly may include a housing inwhich a cutter rotates. It may be desirable to maximize the outerdiameter of the cutter assembly (and with it, the cutter housing) tomaximize the cutting area that may be cut by the cutter assembly. Thesize of the cutter assembly may be limited depending on the intendedintravascular path and the region targeted for treatment, to help reducethe likelihood that the cutter assembly will cut or otherwise damage thevessel wall.

In some of the variations described here, a cutter assembly sized forintroduction through a 7 French guide sheath may have an outer diameterof about 2.4 mm (which, in some variations, may be larger than the outerdiameter of a companion catheter body, as described in more detailabove). A cutter assembly having such an outer diameter may be used, forexample, for access to the larger vessels above the knee (e.g., vesselsbetween about 4 mm and about 7 mm). In other variations described here,a cutter assembly sized for introduction through a 5 or 6 French guidesheath may have an outer diameter of about 1.8 mm to about 2.2 mm(which, in some variations, may be larger than the outer diameter of acompanion catheter body, as described in more detail above). A cutterassembly having such an outer diameter may be used, for example, foraccess to the smaller vessels at or below the knee (e.g., vesselsbetween about 2.5 mm and about 4 mm).

The housing may or may not be dynamic (i.e., able to rotate relative tothe catheter body). In variations where the housing is dynamic, thehousing may be configured to rotate at the same speed or at a differentspeed than the cutter elements. Additionally, the cutter housing may bedynamically driven to rotate in the same direction or in a counterdirection relative to the cutter.

The housing may include one or more imaging assemblies. The imagingassembly may be located on or embedded within the housing. The imagingassembly may cover a portion of the housing, and preferably the imagingassembly circumscribes the housing. The imaging assembly is connected toone or more signal wires that run the length of the atherectomy device.

The leading edge of the cutter housing, which defines the periphery ofthe distal opening through which the cutter projects, may desirably berounded and does not present a sharp distal edge. In these variations, arounded distal housing may reduce the possibility that the peripheraledges of the housing catch on the wall of the guide sheath duringintroduction therethrough. Additionally, a rounded distal edge may alsotend to glance off tissue without grabbing or catching on the tissue,which may minimize the resistance felt by the atherectomy apparatusduring advancement. It should be appreciated that in some variations thecutter housing may have a sharp or beveled distal edge. In some of thesevariations, the cutter housing may have an inner bevel. In othervariations, the cutter housing may have an outer bevel.

In some variations, the outside diameter of the cutter may be less thanthe inside diameter of the cutter housing to create a desired cuttinggap between the two. A larger gap may produce a larger cutting volume,but too large of a gap may permit tissue to enter the cutter housingwhile bypassing the cutter. Representative dimensions will be describedin more detail later. In other variations, the outside diameter of aportion of the cutter may be greater than or equal to the diameter ofthe cutter housing. In these variations, the cutter may cut a largerdiameter of tissue, which may reduce the likelihood that the cutterhousing rubs against tissue during advancement while cutting, therebyfacilitating advancement of the device.

2. The Torque Shaft

The cutter is coupled and rotatable by the torque shaft. The torqueshaft may be, in turn, driven by the motor in the handle. The torqueshaft may be fabricated from any suitable material, preferably one ormore materials that may be consistent with the pushability, pullability,torquability, and trackability of the catheter body, as described above.For example, the torque shaft may comprise a metal braid and/or one ormore metal coils, and one or more portions of the torque shaft embeddedin a polymer, e.g., PEBAX, polyurethane, polyethylene, fluoropolymers,parylene, polyimide, PEEK, and/or PET. In some variations, the torqueshaft may be made from a rigid material such as plastic, renderedflexible by incorporation of a spiral relief or groove.

In some variations (such as the torque shaft depicted above with respectto FIGS. 3A, 3B, 5A and 5B), the torque shaft may comprises a flexiblewire coil wound about a central lumen. The central lumen may be sized toaccommodate the passage of a guide wire therethrough. The flexible wirecoil may preferably be wound in the same direction as the intendeddirection of rotation of the torque shaft, which may cause the coil toopen up if torsional resistance to rotation is encountered (as opposedto clamping down, which may cause the torque shaft to lock on to a guidewire positioned in the central lumen).

Generally, the torque shaft may be coupled to a cutter of a cutterassembly at or near the distal end of the torque shaft, and may beattached to the motor (e.g., by gearing) at or near the proximal end ofthe torque shaft. In some variations (such as the atherectomy apparatusdepicted in FIGS. 3A, 3B, 5A and 5B), the cutter assembly may include acentral lumen that may communicate with the central lumen/guide wirelumen of the torque shaft.

3. The Geometry of the Cutting Elements

As mentioned above, in some variations, the cutter of a cutter assemblymay comprise multiple cutting elements. For example, in the variation ofthe atherectomy apparatus (500) described above with respect to FIGS. 5Aand 5B, the cutter assembly (506) may comprise a cutter having first(512) and second (514) cutting elements. As shown there, the firstcutting element (512) may be positioned distally of second cuttingelement (514). The first cutting element (512) may comprise one or morecutting edges (528) which may at least partially project beyond thedistal end of the cutter housing (510). In some variations, at least aportion of the first cutting element (512) may have a diameter greaterthan or equal to the diameter of the cutter housing (510). The secondcutting element (514) may be at least partially housed within the cutterhousing (510), and may comprise one or more cutting edges (530). Asshown in FIG. 5B, the cutting edges (530) of the second cutting element(514) may be entirely enclosed within the cutter housing (510).Generally, the first (512) and second (514) cutting elements may bephysically coupled together (e.g., by adhesives or welding) for rotationin unison.

The torque shaft may couple to a journal (532) in the second cuttingelement. When the first (512) and second (514) cutting elements arephysically coupled together, the torque shaft may rotate both the firstcutting element and second cutting element in unison. A proximal flange(534) on the second cutting element (514) may be seated within arelieved proximal groove (536) in the cutter housing (510). The relievedproximal groove (536) may serve as an axial retainer for the first (512)and second (514) cutting elements within the cutter housing.

(i) The First Cutting Element

FIGS. 6A-6D depict an illustrative variation of a first cutting element(800) suitable for use with the cutter assemblies described here. Insome variations, the first cutting element (800) may be machined from ahard metallic material (e.g., 440C stainless steel) and may have agenerally hemispherical configuration that includes at least one helicalflute (802) (shown there as a right-hand twist, although it should beappreciated that the at least one helical flute (802) may have aleft-hand twist). While shown in FIGS. 6A-6D as having two helicalflutes (802), it should be appreciated that the first cutting element(800) may comprise any suitable number of helical flutes (802) (e.g.,one, two, three, four, or more helical flutes). Each cutting flute mayform a cutting blade (803) having a cutting edge (804).

The first cutting element may be machined to shape the structure of thehelical flutes (802) within the desired hemispherical geometry. Whensupported in an extended, distally projecting relationship relative tothe cutter housing (e.g., by virtue of the connection to a secondcutting element, as described in more detail above), the hemispherical,fluted geometry may be sized and configured to optimize the capabilityof the cutting blade or blades to cut through and capture occlusivematerials, while minimizing the risk of the cutting blade or bladesgrabbing or digging into tissue, wrapping tissue, and otherwise causingthe motor to stall and overload.

The geometry of each flute may be purposely shaped for theabove-mentioned purposes, and the flute geometry may be characterizedwith reference to a combination of angles (or ranges of angles),comprising a rake angle, a relief angle, a flute angle, and a helixangle. Additionally, while shown in FIGS. 6A-6D as having ahemispherical outer profile, it should be appreciated that the frontcutting element may any external profile, such as an egg-shaped outerprofile.

(a) Rake Angle

For each flute, the rake angle (806) (best shown in FIG. 6C) can bedefined as the angle measured between (i) a radius (808) drawn from therotational axis of the cutting blade (810) to the most radially distantedge (804) of the blade (803) and (ii) a tangent (810) drawn from theinner face of that blade (803). The rake angle may describe the angle ofthe cutting edge (804) relative to the material to be cut.

In some variations, each flute of the first cutting element may possessa positive rake angle (i.e., the inner face of the cutting blade slantsinward or back from the cutting edge). The positive rake angle of eachflute is preferably large, and in some instances may be between greaterthan about 20 degrees. In some of these variations, the rake angle ispreferably greater than about 40 degrees. In some of these variations,the rake angle may be between about 60 degrees and 80 degrees (referredherein as a “high” rake angle). In some variations, the rake angle maybe between 65 degrees and 75 degrees. In some variations, the rake anglemay be about 70 degrees.

Generally, a device having a positive high rake angle may be well suitedfor cutting occlusive materials having less calcium, which may have afibrous, fleshy, and/or rubbery consistency. The rubbery consistency maycause conventional cutters to deflect away from these materials, causingconventional devices to lose trackability, but a high rake angle helps acutter slice into this tissue while minimizing deflection of the cutter.Conventional cutter machining techniques generally cannot produce apositive high rake angle cutter, and these cutters generally have asmall rake angle (less than about 15 degrees). Additionally, a largerrake angle may decrease the structural integrity of a cutter, which maythe cutter more likely to chip or break during use. The cuttersdescribed here, however, may allow for the benefits of high rake anglecutting while reducing the risk of cutter malfunction.

The rake angle of the cutter may be modified depending on the nature ofthe tissue to be cut. For example, a cutter assembly intended to cuthard, calcified occlusive materials having a higher calcium content, maybe configured to have a negative rake angle (i.e., the inner face of thecutting blade may slant outward or forward of the cutting edge), whichmay be well suited for grinding or smashing hardened occlusivematerials. It should be appreciated that a given cutting element can bemachined to incorporate cutting blades having both positive and negativerake angles or otherwise include combination of both cutting andgrinding surfaces. For example, in some variations a cutter may comprisea first cutting element having a plurality of helical flutes, wherein atleast one flute has a cutting edge having a positive rake angle and atleast one flute has a cutting edge having a negative rake angle. In someof these variations, the helical flutes having cutting edges having apositive rake angle may have a positive rake angle greater than about 20degrees (e.g., greater than about 40 degrees or about 70°+/−10°).

In the variation of first cutting element (800) shown in FIGS. 6A-6D,the formation of a flute having a large, positive rake angle (e.g., 70°. . . +−0.10°.) may create a cutting blade having an enlarged concaveinner face. The enlarged concave inner face may define a trough- orscoop-shaped blade that may efficiently slice through the occlusivematerials (812) as shown in FIG. 6D. The large, positive (high) rakeangle and resulting enlarged concave inner face of the cutting blade mayreduce cutting forces and power requirements for the first cuttingelement (800) and may remove large volume of occlusive materials witheach pass of the cutting blade.

(b) Relief Angle

For each flute, the relief angle (814) can be defined as the anglemeasured between (i) the tangent (816) drawn from the most radiallydistant edge (804) of the cutting blade (803) from radius (808) and (ii)the tangent (818) drawn along the outer face of the blade (803). Therelief angle generally spans the gap between the cutting edge (804) andthe occlusive material (812) surface to be cut (such as shown in FIG.6D). Generally, a smaller relief angle may form a more tangentialinterface with a tissue surface during cutting, which may reduce thelikelihood that a cutting edge may snag or otherwise catch on tissueduring cutting. A larger relief angle may provide more aggressivecutting.

Generally, the relief angle is preferably a small angle less than orequal to about 10°. (e.g., between about 0° and about 10°). In some ofthese variations, the relief angle may be about 0°. In some variations,it may be preferable to have a rake angle of about 70 degrees and arelief angle of about 0 degrees. In other variations, a helical flutemay have a rake angle of about 60 degrees and a relief angle of about 10degrees. The formation of a flute with a small relief angle may create acutting edge (804) that may make aggressive contact with the occlusivematerials (812) such as shown in FIG. 6D. Together with a large positive(high) rake angle, a small relief angle may lead to highly efficientcutting and capture of occlusive materials at the distal end of thecutter assembly, minimizing residue and embolization.

(c) Flute Angle

For each flute, the flute angle (824) can be defined in terms of arelationship with the rake angle and the relief angle, as follows: FluteAngle=90°−(Rake Angle)−(Relief Angle)

The magnitude of the flute angle is an indication of how thick and sharpthe cutting edge is. Given that, in a preferred embodiment, the rakeangle may be in a range between about 60°, and 80°; the relief angle maybe in a range between of about 0° and 10°, the flute angle may be inrange between about 0° and about 30°. Maximizing the rake angle andminimizing the relief angle to achieve efficient cutting conditions mayresult in a cutter geometry having a reduced flute angle. Accordingly,it may be desirable that the first cutting element be machined from ahard metallic material to include at a cutting edge that is a sharp aspossible. In some variations, is may also be desirable to coat thecutting blade with a biocompatible, highly lubricious material with alow coefficient of friction (preferably no greater than 0.5) to helpkeep the cutting blade sharp during use. In these variations, coatingmaterials such as titanium nitride or diamond-like carbon (DLC) may beused.

(d) Helix Angle

In the variation of the first cutting element (800) shown in FIGS.6A-6D, each flute (802) of the first cutting element (800) may comprisea helical cut. The helix angle (826) may be defined as the angle between(i) the rotational axis (828) of the cutting blade (803) and (ii) atangent (830) drawn along the inner face the cutting blade (803). Themagnitude of the helix angle is indicative of the capability of thecutting blade to transport cut occlusive material proximally along thecutting blade and into the housing.

In some variations, each flute (802) of the first cutting element (800)may have a helix angle (802) between about 30° and 60°. A helix anglebelow 30° may increase the likelihood the first cutting element (800)may overload with occlusive material and stall, while a helix angleabove 60° may diminish the cutting efficiency of the first cuttingelement (800).

FIGS. 8A-8C illustrate the first cutting element according otherembodiments. As shown in FIG. 8A-8C, the cutting element may include oneor more blades 1110, one or more blunt crushing elements 1008, or both.The one or more blades 1110 may be designed with the angle geometriesdiscussed above. The blades 1110 are designed to cut through theocclusion as the cutting element is rotated. The crushing elements 1008are designed to deliver a crushing blow to the occlusion. That is, thecrushing elements 1008 are designed to deliver a blow or sudden impactto the occlusion that further breaks up the occlusion beyond what ispossible with the blades 1110 alone. Particularly, the crushing elements1008 are useful in breaking through fibrous plaque and highly organizedthrombi. The crushing elements 1008 are preferably blunt andsubstantially rectangular in shape. In certain embodiments, the crushingelements 1008 form a zero rake angle or a negative rake angle (asopposed to the positive rake angle of the blades 1110). The negativerake angle may range from at least 1, 5, 10, 15, 20, 25 30 degrees ormore. Although, the crushing elements 1008 may include other shapes,such as spherical, triangular, cylindrical, hexagonal, etc. While thebody of a crushing element is generally blunt, the edges of the crushingelement may be sharp to also assist in cutting through the occlusion.The one or more crushing elements 1008 may be located between the blades1110 (as shown in FIGS. 8A-8C). In certain embodiments, the crushingelements 1008 are formed from a different material than the rest of thecutting element. The crushing elements 1008 are ideally formed fromcarbide metal, such as titanium carbide.

(ii) The Second Cutting Element

As mentioned above, the cutter assembly may comprise a second cuttingelement. For example, in the variation of atherectomy apparatus (500)shown in FIGS. 5A and 5B, the cutter assembly (506) may comprise asecond cutting element (514). In variations that include a secondcutting element, the second cutting element may be machined from a hardmetallic material (e.g., 17-4 stainless) to include helical cuttingflutes. The cutting flutes may be configured to have the same rakeangle, relief angle, flute angle, and helix angle as the flutes of thefirst cutting element. In some variations, the above-mentionedgeometries of the first and second cutting elements may be identical,except that the second cutting element has more flutes than the firstcutting element. In some of these variations, the second cutting elementmay have double the number of flutes of the first cutting element; thatis, four flutes are shown.

In some variations, the second cutting element is machined to include ahollow stem that fits within a center journal of the first cuttingelement. For example, in the variation of the atherectomy apparatusshown in FIGS. 5A and 5B, the second cutting element (514) may include astem (538) around which the first cutting element (512) can be placed.For example, FIG. 9 shows a perspective view of cutter assembly (506),in which the first (512) and second (514) cutting elements may be joinedtogether (e.g., by adhesive or welding) in a rotationally alignedcondition. In the aligned condition, two opposing cutting flutes (540)of the second cutting element (514) may be rotationally aligned with thetwo opposing cutting flutes (542) of the first cutting element (512).Their geometries may be matched during machining, and may act to cut andconveyed occlusive material proximally by the first cutting element intothe housing and further convey the occlusive material more proximallyinto contact with the additional cutting blades of the second cuttingelement.

-   -   (iii) Two-Stage Cutting Action

The cutter assembly (506) shown in FIG. 7 may provide a two-stagecutting action. Generally, the first cutting element (512) may cutocclusive material and convey the material to the second cutting element(514). The second cutting element (514) may further cut or macerate theocclusive materials into smaller particles. During both cutting actions,the occlusive materials may be continuously captured within the housingand conveyed proximally away from the targeted intravascular site. Whenthe first and second cutter elements rotate, the helical cuttingsurfaces formed by the flutes may cut occlusive materials in the bloodvessel and may convey the occlusive material from the blood vessel intothe housing through the action of the helical flutes, and may do sowithout the assistance of any vacuum aspiration.

D. Mechanical Removal of Occlusive Materials

As mentioned above, in some variations of the atherectomy apparatusesdescribed here, the atherectomy apparatus includes an internal conveyingmember. For example, the variation of atherectomy apparatus (500) shownin FIGS. 5A and 5B may comprise an internal conveyor (524). Invariations that include an internal conveying member, the internalconveying member may comprises a wire helically wound about the torqueshaft in a direction common with the helical cutting surfaces of thecutter assembly. The cross-section of the internal conveyer member maybe substantially circular or rectangular in shape. FIG. 9A illustratesthe internal conveying member with a circular cross-section and FIG. 9Billustrates the internal conveying member with a rectangularcross-section. A rectangular cross-section may increase the amount ofcontact between the conveyer and the internal surface of the catheterbody, thereby increasing the conveying member's ability to move blockageparticles down the length of the catheter. When a cutter assembly cutsand captures occlusive material (e.g., when the helical flutes of afirst and/or second cutting element conveys cut and captured occlusivematerials to the conveying member), the conveying member may rotate incommon with a torque shaft to convey the cut and captures occlusivematerials it receives from the cutter assembly further back (proximally)along the catheter body into the handle. For example, FIG. 10 shows thevariation of atherectomy apparatus (500) described above with respect toFIGS. 5A and 5B conveying and transferring occlusive material (1700)proximally through the apparatus.

The occlusive materials carried back by the conveying element into thehandle may be transferred into a discharge passage within the handle. Atransfer propeller communicating with the discharge passage may becoupled to the torque shaft to rotate in common with the torque shaft,and may act to pump the cut, captured, and conveyed occlusive materialsinto the discharge passage. The discharge passage may include anexternal coupler (e.g., a leur connector) to couple the dischargepassage to an external waste container. The cut and captured occlusivematerials may be conveyed into the waste receptacle, and may be done sowithout need for vacuum aspiration. For example, as shown in FIG. 10,atherectomy apparatus (500) may comprise a transfer propeller (544), adischarge passage (546), and an external coupler (548), which may beconnected to an external waste container (1702) as just described.

In some instances, it may be desirable to convey saline or anotherbiocompatible fluid down the catheter body for mixing with occlusivematerial within the cutter assembly. Mixing the fluid with the occlusivematerials may form a slurry, which may reduce the viscosity of thematerials cut, captured, and conveyed from the vessel by the atherectomyapparatus. This may reduce the load imposed on the cutter assembly andfacilitate the transfer of materials into the waste receptacle. As shownin FIG. 10, the atherectomy apparatus (500) may convey a fluid (1704)from the distal end of the device. In some variations, the fluid (1704)may be conveyed through an internal/guide wire lumen within the torqueshaft (522).

II. Deflectable Atherectomy Systems and Apparatuses

A. Overview

In some variations, the atherectomy systems described here may comprisean atherectomy apparatus configured to selectively dynamically deflectat its distal end (e.g., near a cutter assembly). For example, FIGS.11A-11D show one variation of an atherectomy apparatus (1800) comprisinga handle (1802), a catheter body (1804), and cutter assembly (1806).These elements may include any of the features previously described. Aswill be described in greater detail, the catheter body (1804) may beconfigured to dynamically deflect at its distal end (where the cutterassembly (1806) is carried) relative the central axis of the proximalcatheter body (1804), as shown in FIG. 11C. This deflection may occurwithout axial advancement of the atherectomy apparatus. Additionally,the atherectomy apparatus (1800) may be configured to rotate the distalend of the apparatus while deflected about the central axis of theproximal catheter body (1804) to sweep the cutter assembly (1806) in anarc (1808) around the central axis, as shown in FIG. 11D. The ability ofthe atherectomy apparatus (1800) to sweep may allow for the cutterassembly to cut occlusive materials in a region larger than the outsidediameter of the cutter assembly, as will be described in more detailbelow.

The atherectomy apparatus (1800) may be used in an atherectomy systemincluding a guide wire (1810), and may be introduced into a blood vesselfrom an external percutaneous access site such as described previouslywith respect in FIGS. 4A-4D. The handle (1802) may be sized andconfigured to be securely held and manipulated by a caregiver outside anintravascular path in a manner previously described to advance thecatheter along an intravascular. Image guidance (e.g., CT, radiographic,or guidance mechanisms, or combinations thereof), may be used to aid thecaregiver's manipulation.

FIGS. 11A and 11B depict a variation of an atherectomy apparatus (2000)configured for use with the atherectomy systems described here. As shownthere, atherectomy apparatus (2000) may comprise a handle (2002), acatheter assembly (2004), and a cutter assembly (2006). As shown there,the cutter assembly (2006) may comprise a ferrule (2008), a cutterhousing (2010), a first cutting element (2012), and a second cuttingelement (2014). The cutting assemblies may have any elements orcombination of elements as described in more detail above. For example,the cutter housing (2010), first cutting element (2012), and secondcutting element (2014) may have any of the elements and dimensionspreviously described. In some variations, the first and second cuttingelements may each comprise one or more helical cutting flutes having arake angle between about 60 degrees and 80 degrees, a rake angle lessthan or equal to 10 degrees (in some of these variations, about 0degrees), a flute angle between about 30 degrees and about 0 degrees,and a helix angle between about 30 degrees and about 60 degrees.

Also shown in FIGS. 12A and 12B, the atherectomy apparatus (2000) mayfurther comprise a drive motor (2016), which in some variations may becontained within a housing (2018) of the handle (2002). Also shown thereis a torque shaft (2020) which may be coupled by gearing to the motor(2016) at a proximal end of the torque shaft (2020) and coupled to thesecond cutting element (2014) at a distal end of the torque shaft(2020). The torque shaft rotates the first (2012) and second (2014)cutting elements relative to the cutting assembly, such as described inmore detail above. When the cutter rotates, it may cut and conveyocclusive materials into the cutter housing (2010), and may do sowithout the use of any vacuum aspiration.

The cutter housing (2010) may include an imaging assembly (2011) locatedthereon or embedded therein. The imaging assembly (2011) may be used toobtain real-time images of the occlusion (atheroma, plaque, thrombi, oremboli) prior to morcellation with the cutter (2012), duringmorcellation, and after morcellation to observe completeness of theprocedure or whether more cutting is necessary to remove the blockageentirely or regain a suitable luminal opening. Suitable imagingassemblies include optical-acoustic imaging apparatus, intravascularultrasound (IVUS), forward-looking intravascular ultrasound (FLIVUS) oroptical coherence tomography (OCT). Preferably, the imaging assembly(2011) is an ultrasound-based imaging assembly. The ultrasound imagingassembly may be a phased-array assembly, which includes a plurality oftransducer elements. The imaging assembly (2011) may located/embedded ona portion of the housing (2010). In certain embodiments, the imagingassembly (2011) circumscribes the housing (314). In other embodiments,the imaging assembly (2011) is located on the catheter assembly (2032)proximal to the housing (2010). The imaging assembly 2011 is connectedto one or more signal wires (2013), which are in turn connected to asignal processing apparatus. The signal wires (2013) transmit energy tothe imaging assembly 2011 to emit imaging signals (such as ultrasound oroptical signals) and transmit back signals (back-echos) received fromthe imaging assembly to a signal processing apparatus and imagingconsole. The signal wires (2011) may run alongside an inner surface ofthe catheter assembly (2036) to the signal processing apparatus, or thesignal wires (2011) may be incorporated into the catheter assembly(2036). In certain embodiments, the catheter assembly (2036) may definea separate lumen through which the signal wires (2013) may be routed.

The atherectomy apparatus (2000) may also further comprise an internalconveyor (2024), which may convey the occlusive materials from thecutter housing (2010) further back (proximally) along the catheter bodyfor discharge outside the patient's body. In these variations, there maybe no need for use of a vacuum pump.

The individual components of the systems shown in FIGS. 11 and 12 arediscussed in more detail hereinafter.

B. The Catheter Body

1. Overview

As mentioned previously, the atherectomy apparatus (2000) may comprise acatheter assembly (2004). The catheter assembly may have any suitabledimensions, such as described in more detail above. For example, in somevariations, the catheter assembly (2004) may have an outer diameter lessthan or equal to the outer diameter of the cutter assembly (2006), Insome of these variations, the catheter assembly (2004) may have an outerdiameter less than the outer diameter of the cutter assembly (2006). Insome of these variations, a cutter assembly may have an outer diameterof 2.4 mm, and the catheter assembly may have an outer diameter of 2.2mm. The catheter assembly may be configured to balance the columnstiffness (pushability), tensile stiffness (pullability), torsionalstiffness (torquability), and bending stiffness (trackability) of thecatheter assembly, such as described in more detail below.

The catheter assembly (2004) may comprise an outer catheter shaft(2026), an inner catheter shaft (2028), and a sweep tube assemblycomprising an inner sweep tube (2030) and an outer sweep tube (2032).

2. The Outer Catheter Shaft

The outer catheter shaft (2026) may be formed in any suitable manner.For example, the outer catheter shaft (2026) may be formed from a metaltube (e.g., a 304 stainless steel tube). The outer catheter shaft (2026)may have any suitable dimensions. For example, in some variations it maybe desirable for the outer catheter shaft (2026) to be formed from atube having an outside diameter of about 2.2 mm, a wall thickness ofabout 0.288 mm, and a length of about 1347 mm (53.03 inches).

As discussed previously, a metal tube with some or all of the dimensionsdescribed immediately above may provide a high degree of pushability,pullability, and torquability, the baseline bending stiffness may limitthe trackability of the catheter body given the length of the catheterbody. Accordingly, in some variations, the bending stiffness of themetal tube may be incrementally modulated along the length of thecatheter body by creating zones of cut patterns along at least a portionof the length of the catheter body. The cut patterns may be formed inany suitable manner (e.g., via laser cutting), and the zones may imparta desired profile of bending stiffness over the length of the catheterbody. For example, cut pattern zones may be used to incrementallydecrease the bending stiffness in a stepwise fashion from proximal endto distal end, to provide a minimum bending stiffness conducive totrackability at the distal end (where trackability is more desirable).The stepwise fashion in which the bending stiffness is decreased may beconfigured in a manner to help maintain the overall pushability,pullability, and torquability.

The catheter bodies may have any number of zones/regions havingdifferent cut patterns (or in some zones, no cut pattern at all). Incertain embodiments, one or more zones of the catheter body includehelical cut patterns, threaded cut patterns, spiral cut patterns, orbrickwork cut patterns. As mentioned above, the outer catheter shaft canbe lined or jacketed with a polymeric material, and further may betreated to produce hydrophilic, hydrophobic, or drug binding (heparin,antimicrobial) properties.

3. The Sweep Tube Assembly

As mentioned above, the catheter assembly (2004) shown above in FIGS.12A and 12B may comprise a sweep assembly comprising an outer sweep tube(2032) and an inner sweep tube (2030). The outer sweep tube (2032) maybe connected to the distal end of the outer catheter shaft (2026) (e.g.,via coupler (2036)) at a proximal end of the outer sweep tube (2032),and may be connected to the cutter assembly (2006) at a distal end ofthe outer sweep tube (2032).

As will be described in greater detail below, within the outer sweeptube (2032), the inner catheter shaft (2028) may be coupled to theproximal end of the inner sweep tube (2030) (e.g., via inner coupler(2038)). Sliding the inner catheter shaft (2028) in a distal directionmay cause the inner sweep tube (2030) to preferentially bend away fromthe center axis, thereby preferentially deflecting the cutter assemblytoward a side wall of the vessel.

(a) The Outer Sweep Tube

The outer sweep tube (2032) may be formed from a metal tube (e.g., 304stainless steel). As mentioned above the outer sweep tube (2032) mayhave a distal sweep portion (2034) and a proximal post portion (2036).The distal sweep portion (2034) and the proximal post portion (2036) maybe formed from a single tube, or may be formed separately and joined(e.g., by spot welding). The distal sweep portion (2034) and proximalpost portion (2036) may have any suitable lengths. In some variations,the distal sweep portion (2034) may have an axial length of about 0.450inches and the proximal post portion (2036) may have an axial length ofabout 0.400 inches.

In some variations, the proximal post portion (2036) may comprise a cutpattern (such as one or more of the patterns described above) todecrease the bending stiffness of the proximal post portion (2036). Insome of these variations, the proximal post portion (2036) may comprisea 135° cut/45° uncut alternating brickwork pattern with a pitch of about0.12 inches. The highly flexible nature of such a two-post pattern mayprovide a flexible transition between the outer catheter body (2026) andthe distal sweep portion (2034) of the outer sweep tube (2032).

The distal sweep portion (2034), conversely, may be configured to imparta preferential bending property in a predetermined direction. In somevariations, the distal sweep portion (2034) may comprise a pattern ofclosed, interlocking cuts (which may be laser cut). In the variationshown in FIGS. 12A, 12B, the closed, interlocking cuts (2038) may extendin rows that extend around a majority of the circumference (e.g., 350°)of the outer sweep tube, which may leaving a spine (2040) of uncutmaterial (e.g., about 10° of uncut material) that extends axially alongthe distal sweep portion (2034).

In some variations, the interlocking cuts (2038) may comprise chamfereddovetail cuts. These cuts may provide a plurality of rows of materialextending from the spine (2040). The rows (which may have an maximumuncut length of 0.25″ each) may be separated by about 0.007 inches ofchamfered, dovetail cuts (at 67.4°). The interlocking cuts (2038) mayhave any number of dovetail cuts (e.g., twelve dovetail cuts along thecircumference in each row). In some variations, the distal sweep portion(2034) may include with a proximal uncut region (adjacent the proximalpost portion (2036), which may be about 0.01 inches in length) and adistal uncut region (adjacent the cutter assembly, which may be betweenabout 0.025 inches to 0.35 inches). Additionally, in some variations atab (2042) of uncut material may extend beyond the distal end inalignment with the spine (2040), which may form an outer tube alignmentkey, as will be described in greater detail later.

The laser-formed pattern of closed, interlocking cuts as just describedmay resist bending in any direction except in the direction of the spine(2040). When a bending force is applied, the interlocking cuts open topermit the bending to occur in the direction of the spine. Bending forcein any other direction may be resisted, as the interlocking cuts areclosed to resist bending in these directions.

(b) The Inner Sweep Tube

The inner sweep tube (2030) may be fabricated from a metal tube formed(e.g., nitinol). The inner sweep tube (2030) may extend axially withinthe outer sweep tube (2032) and may have any suitable dimensions. Forexample, in some variations the inner sweep tube (2030) may have anouter diameter of about 0.068 inches and an inner diameter of about0.058 inches, and may have a total axial length of about 0.700inches.+−0.0.005 inches.

In some variations, the baseline bending stiffness of the inner sweeptube (2030) may be reduced to impart a preferential bending property ina predetermined direction. In some of these variations, preferentialbending may be created using a pattern of open, dovetail cuts (2048). Inthe variation shown in FIGS. 12A, 12B, and 13A-13D, the closed, open,dovetail cuts (2048) may extend around a majority of the circumference(e.g., 350°) of the inner sweep tube (2030), which may leaving a spine(2050) of uncut material (e.g., about 10° of uncut material) thatextends axially along the inner sweep tube (2030). As shown in FIG. 13A,the spine (2040) of the outer sweep tube (2032) and the spine (2050) ofthe inner sweep tube (2030) may be aligned such that spine (2040) andspine (2050) may be positioned on opposite sides of the catheterassembly.

The dovetail cuts (2048) may have any suitable dimensions. For example,in some variations the dovetail cuts (2048) each extend about 0.55inches along the axis of the inner sweep tube (2030), and may includeany number of dovetail cuts (2048). In some of these variations, theinner sweep tube (2030) may comprise eight dovetail cuts, which mayextend about 0.60″ along the spine (2050). Additionally, in somevariations a tab (2052) of uncut material may extend beyond the distalend in alignment with the spine (2050), which may form an inner tubealignment key, as will be described in greater detail later.

The laser-formed pattern of open cuts as just described permitpreferential bending in the direction of the open cuts, away from thespine, until the open cuts come together and interfere in a distal toproximal succession. When a bending force is applied thereto, the opencuts may permit bending, but, as the bending continues, may resistbending as cuts close and interfere. A preformed bending radius maythereby be built into the inner sweep tube.

The inner sweep tube is inserted into the outer sweep tube, and theinner (2052) and outer alignment tabs (2042) may be brought intoregistration (see FIGS. 13A and 13B). The rotationally aligned inner(2052) and outer (2042) tabs may be fitted into an alignment key (2054)on the ferrule (2008) (as shown in FIG. 13B). This fitting may ensurethat the inner and outer sweep tubes may be properly aligned, and mayalso act to prevent relative rotation between the inner and outer sweeptubes. In some variations, and the inner and outer sweep tubes may befixed to the proximal end of the ferrule (e.g., by welding). Asmentioned above (and as shown in FIG. 13A), when the inner (2052) andouter (2042) tabs are rotationally aligned, the spine of the outer sweeptube (2042) may axially aligned with the open cuts (2048) of the innersweep tube (2030) (i.e., the spine (2050) of the inner sweep tube (2030)may rotationally spaced 180° from the spine (2040) of the outer sweeptube (2032)).

As FIG. 13A also shows, the proximal end of the inner sweep tube (2030)may include includes an open boot region (2054) facing at an angle(e.g., about 90°) from the pattern of open dovetail cuts. The open bootregion (2054) may be sized and configured to receive the distal end ofthe inner catheter shaft. It is the inner catheter shaft that may applya bending force to the deflecting assemblage, as will be described ingreater detail later.

(iii) The Inner Catheter Shaft

The inner catheter shaft (2028) of the atherectomy apparatus (2000)shown in FIGS. 12A and 12B may be sized and configured and fabricated ingenerally the same manner as any of the catheter bodies previouslydescribed (e.g., such as the catheter bodies described above). Forexample, the inner catheter shaft (2028) may be formed from a metal tube(e.g., a 304 stainless steel tube), and may have dimensions suitable toallow the inner catheter shaft (2028) to fit within the outer cathetershaft and to accommodate passage of the torque shaft and conveyorelement therein. Representative embodiments will be described.

The tube of this material and configuration will provide a baselinecolumn stiffness, tensile stiffness, torsional stiffness, and bendingstiffness. In some variations, the bending stiffness of the metal tubemay be incrementally modulated along the length of the catheter body bycreating zones of cut patterns along at least a portion of the length ofthe catheter body. The cut patterns may be formed in any suitable manner(e.g., via laser cutting), and the zones may impart a desired profile ofbending stiffness over the length of the catheter body. For example, cutpattern zones may be used to incrementally decrease the bendingstiffness in a stepwise fashion from proximal end to distal end, toprovide a minimum bending stiffness conducive to trackability at thedistal end (where trackability is more desirable). The stepwise fashionin which the bending stiffness is decreased may be configured in amanner to help maintain the overall pushability, pullability, andtorquability.

In some instances, there may be a gap between the inner and outercatheter such shafts, such that flushing fluid that may be conveyed downto the cutter assembly, for mixing with occlusive material within thecutter assembly. Mixing the fluid with the occlusive materials may forma slurry, which may reduce the viscosity of the materials cut, captured,and conveyed from the vessel by the atherectomy apparatus to reduce theload imposed on the cutter assembly and facilitate the transfer ofmaterials into the waste receptacle, as has been previously described.An increased gap may provide a greater volume of fluid to the cutterassembly, which may in turn improve the mechanical conveyance ofocclusive materials away from the long total occlusion, thereby reducingthe chance of cutter overload and stalling.

(iv) The Mechanism of Deflection and Sweep

The distal end of the inner catheter shaft may be coupled to the innersweep tube, and may control deflection of the catheter assembly. Forexample, in the variation of atherectomy apparatus (2000) describedabove with respect to FIGS. 12A, 12B, 13A and 13B, the inner coupler(2038) may connect the inner catheter shaft (2028) to the inner sweeptube (2030) via the boot region (2054). Generally, the inner coupler(2038) may join the inner catheter shaft (2028) to the boot region(2054) in a manner that may transmit axial compression or tensile forcesto the inner sweep tube (2030), but accommodates relative rotationbetween the inner catheter shaft (2028) and the inner sweep tube (2028)(i.e., the inner catheter shaft does not rotate when the outer cathetershaft is rotated to rotate the inner and outer sweep tubes).

In the situation where the diameter of the inner catheter shaft isreduced to increase the gap dimension between the inner catheter shaftand the outer catheter shaft (as previously described, to accommodate agreater fluid volume), the coupling sleeve may be sized to locallystep-up the distal diameter of the reduced diameter inner catheter shaftwhere it is coupled to the open boot of the inner sweep sleeve (i.e.,the inner sweep tube need not be downsized when the inner catheter shaftis downsized), but it should be appreciated that in some instances thediameters of these components may be the same.

The proximal end of the inner catheter shaft may be coupled to a controlknob (2056) on the handle (2002). The control knob (2056) may beadvanced axially (distally) to advance the inner catheter shaft (2028)against the inner sweep tube (2030), to thereby apply a compressiveforce (as illustrated by arrow (2058) in FIG. 13D) along the innercatheter shaft (2028) to the inner sweep tube (2030). Being constrainedfrom axial advancement by the ferrule (2008), the inner sweep tube maypreferentially deflect in response to the applied compressive force inthe direction of the open cut regions (as illustrated by arrow (2060) inFIG. 13D). Likewise, the control knob may be retracted axially(proximally) to relieve the compression force and apply a tensile forceto the inner sweep tube, to straighten the delectable assembly, as shownin FIG. 13C.

As shown in FIGS. 13C and 13D, with the spine of the inner sweep tubealigned opposite the spine of the outer sweep tube, the preferentialbending property of the inner sweep tube (in the direction of the opencuts) may be unified with the preferential bending property of theconcentric outer sweep tube (in the direction of the spine, away fromthe close cuts). The inner sweep tube may progressively bend in responseto the bending force imparted by axial advancement of the inner cathetershaft, which may cause the open cuts of the inner sweep tube close andinterfere first at the distal end, followed in succession by closing andinterference of the proximal cuts down the length of the inner sweeptube. This may form a progressive distal-to-proximal stacking pattern asthe inner sweep tube progressively bends until all cuts on the innersweep tube close and interfere to define the full bend radius (which insome variations may be about 1°). The outer sweep tube may bend inconcert with the inner sweep tube, which may open the closed cuts in adistal-to-proximal stacking pattern. The inner and outer sweep tubes maychannel the applied bending force in the direction of preferentialbending, and may require less bending force for a given angular unit ofdeflection. Further, the successive distal-to-proximal stacking of theinner sweep tube cuts and opening of the outer sweep tube cuts mayresult in a uniform column stiffness applied to the cutter assemblyregardless of the degree of deflection.

When deflected, the catheter assembly may apply an apposition force uponthe cutter assembly, which may be created by opposing contact of theouter catheter assembly against an opposite vessel wall when the cutterassembly (deflected at the end of the catheter) contacts the occlusivematerials at a desirable attack angle (as shown FIGS. 19B and 19C). Theunified cooperation of the inner and outer sweep tubes duringpreferential bending may increase the magnitude of the apposition force,and may improve trackability and avoid trauma during advancement overthe guide wire.

In some variations, the outer catheter shaft may be coupled to a post onthe handle that may be sized and configured to rotate in response torotation of the control knob (2056). While axial advancement of thecontrol knob (2056) applies compressive force to the inner cathetershaft to deflect the cutter assembly (as described in more detailabove), rotation of the control knob (2056) may apply a torque to theouter catheter shaft to rotate the cutter assembly. The cutter assemblymay sweep in an arc within the vessel, to clear a diameter of occlusivematerials that is greater than the outer diameter of the cutterassembly. It may also be possible to apply torque to the outer cathetershaft by rotating the handle itself. Selective rotation of the cutterassembly can thus be finely controlled by a combination of control knobmanipulation and handle twisting.

An indexing mechanism may be provided to provide stepwise control ofdeflection and/or sweeping, with tactile and/or audible feedback, sothat a user may maintain knowledge of the rotation.

(v) Passive and Active Steering

The enhanced, preferential bending properties of the trackable,deflectable catheter assembly may provide the capability to bothactively and passively steer the atherectomy apparatus through tortuousintravascular anatomy. FIGS. 14A-14F(5) depict a manner by which theatherectomy apparatus (2000) described above in relation to FIGS. 12Aand 12B may be actively and passively steered within a vessel.

Active steering may be accomplished by advancement of the inner cathetershaft to bend the distal catheter assembly, accompanied by rotation ofthe catheter assembly, to point the cutter assembly in a preferreddirection through an intravascular path, with or without a guide wire,and/or to point the cutter assembly toward a side wall of a vessel, withapposition, to cut and capture occlusive materials. For example, thecutter assembly (2006) of atherectomy apparatus (2000) may be advancedinto occlusive material (1900) in a vessel (1902), as shown in FIG. 14A.When in place in the vessel, the catheter assembly (2004) may bedeflected as shown in FIG. 14B. The deflected catheter assembly (2004)may be rotated to sweep the cutter assembly (2006), as shown in FIGS.14C and 14D. This sweep may cause the cutter assembly to move in an arcthat is greater than the outer diameter of the cutter assembly. In somevariations, the cutter assembly (2006) may cut in a diameter (D2 asshown in FIG. 14E) at least two times the diameter of the cutterassembly (D1 as shown in FIG. 14E). In other variations, the cutterassembly (2006) may cut in a diameter (D3 as shown in FIG. 14E) at leastthree times the diameter of the cutter assembly. In still othervariations, the cutter assembly (2006) may cut in a diameter (D4 asshown in FIG. 14E) at least four times the diameter of the cutterassembly.

Passive steering may be accomplished without advancement of the innercatheter shaft, when the cutter assembly (2006) encounters a bend in theintravascular path (see FIG. 14F-1). Once the cutter assembly approachesor contacts the bend, the caregiver may rotate the outer catheter body(and thus the deflected catheter assembly) into an orientation in whichthe preferential deflection direction faces away from the inside radiusof the bend (see FIGS. 14F-2 and 14F-3). In the representativeembodiment, this orientation may face the alignment key (2054) on theferrule away from the inner radius of the bend (as can be seen in FIG.14F-3). Due to the preferential bending properties of the catheterassembly when in this orientation, subsequent advancement of the outercatheter shaft, without concurrent advancement of the inner cathetershaft, may apply enough compression force to cause deflection of thecatheter assembly in the preferential direction (i.e., away from theinside radius of the bend). Continuance of the compression force uponthe catheter body may cause the catheter body to follow the passivelydeflected catheter assembly away from inside radius of the bend and intothe bend itself (see FIGS. 14F-3 and 14F-4).

Successive bends in a tortuous path may be navigated in the same passivemanner, by rotating the catheter body at each successive bend (e.g., byrotating the control knob or by rotation of the handle itself) to orientthe preferential deflection of the catheter assembly away from therespective inner bend radius, and without the need to actively steer bymanipulation of the inner catheter shaft.

In some variations, the catheter assembly (2004) may include one or moreradiographic markings to indicate during radiographic guidance theorientation of the preferential bend direction of the catheter assembly,whether left, or right, or toward the viewer, or away from the viewer.al position of the cutter assembly without taking their eye off theradiographic image.

FIGS. 15A and 15B depict another variation of an atherectomy apparatus(1600) described here. As shown there, atherectomy apparatus (1600) maycomprise a first catheter (1602), a second catheter (1604), and a cutterassembly (1605) attached to the first catheter (1602). The firstcatheter (1602) may be moveable relative to the second catheter (1604)to move a distal portion of the atherectomy apparatus (1600) between anundeflected configuration (as shown in FIG. 15A) and a deflectedconfiguration (as shown in FIG. 15B). In the variation of atherectomyapparatus (1600) shown in FIGS. 15A and 15B, the first catheter (1602)may be moveable within the second catheter (1604), although it should beappreciated that in other variations the second catheter (1604) may beslidable within the first catheter (1602).

Generally, a distal portion (1606) of the second catheter (1604) may beshaped to take on a deflected position as shown in FIG. 15B.Specifically, the deflected distal portion (1606) may comprise a doublecurve having a first proximal curve (1608) and a second distal curve(1610). As shown there, the first curve (1608) may bend the distalportion (1606) away from the longitudinal axis (1612) of a proximalportion of the second catheter (1604), while the second curve (1610) maybend the distal portion (1606) in a direction toward the longitudinalaxis (1612). The double-curve configuration of the distal portion (1606)may allow the second curve (1610) to contact or otherwise rest against awall (1614) of a blood vessel (1616), as shown in FIG. 15B.Additionally, this may angle the cutter assembly (1605) toward anopposite vessel wall (1618) during cutting. In instances when theatherectomy apparatus (1600) is advanced over a guide wire (1620) asshown in FIG. 15B, the guide wire (1620) may contact the opposite vesselwall (1618) and may help to prevent the cutter assembly (1605) fromdirectly contacting and/or damaging the vessel wall (1618). In someinstances, the double-curve configuration of the distal portion (1606)may allow for advancement of the distal portion (1606) while deflectedwhile minimizing the risk that the cutter assembly (1605) may catch ontissue and retroflex.

As mentioned above, the first catheter (1602) may be moved relative tothe second catheter (1604) to move the atherectomy apparatus betweendeflected and undeflected configurations. Specifically, the firstcatheter (1602) may comprise a distal portion (1622) and a proximalportion (not shown), where the distal portion (1622) is more flexiblethan the proximal portion. Additionally, the distal portion (1622) ofthe first catheter (1602) may be more flexible than the distal portion(1606) of the second catheter (1604), while the proximal portion of thefirst catheter (1602) may be stiffer than the distal portion (1606) ofthe second catheter (1604). Accordingly, the first catheter (1602) maybe advanced such that the flexible distal portion (1622) of the firstcatheter (1602) extends beyond the distal end of the second catheter(1604), which may the proximal portion of the first catheter (1602)within the distal portion (1606) of the second catheter (1604) (oraround the distal portion (1606) of the second catheter (1604) invariations where the second catheter (1604) is positioned inside thefirst catheter (1602). Because the proximal portion of the firstcatheter (1602) is stiffer than the distal portion of the secondcatheter (1604), axial alignment of these catheter segments may causethe proximal portion of the first catheter (1602) to straighten out thecurves of the distal portion of the second catheter (1604), therebyplacing the atherectomy apparatus (1600) in an undeflectedconfiguration, as shown in FIG. 15A. Because the flexible distal portionof the first catheter (1602) extends beyond the distal portion of thesecond catheter (1604) when in an undeflected configuration, it may beused to track the cutter assembly (1605) along a guide wire duringnavigation of the atherectomy apparatus (1600) through the vasculature.Additionally, the atherectomy apparatus (1600) may be advanced whilecutting to cut along the path of the guide wire (which may be a straightpath in some instances), as described in more detail below. Theatherectomy apparatus (1600) may then be withdrawn and deflected to cuta larger path through occlusive material (not shown), such as describedbelow.

To move the atherectomy apparatus to a deflected configuration, thefirst catheter (1602) may be withdrawn to place the flexible distalportion (1622) of the first catheter (1602) in axial alignment with thedistal portion (1606) of the second catheter (1604). Because the distalportion (1606) of the second catheter (1604) is stiffer than the distalportion (1622) of the first catheter (1602), the second catheter (1604)may cause the flexible distal portion (1622) of the first catheter(1602) to take on the dual-curve configuration described above withrespect to FIG. 15B.

III. Imaging Assemblies for Use with Atherectomy Devices

Atherectomy systems of the invention include an imaging assembly (e.g.,311, 511, 2011) that provides for guided cutting and removal ofocclusions. The imaging assembly may be and ultrasound imaging assembly,photoacoustic imaging assembly, optical coherence tomography imagingassembly, or combination thereof. In advanced embodiments, the systemsof the invention incorporate focused acoustic computed tomography(FACT), which is described in WO2014/109879.

The imaging assembly may be an intravascular ultrasound (IVUS) imagingassembly. The ultrasound probe can either be either a rotatingtransducer or an array of circumferentially positioned transducers. Theproximal end of the catheter is attached to computerized imagingconsole. The IVUS imaging element (i.e. ultrasound probe) includestransducers that image the tissue with ultrasound energy (e.g., 20-50MHz range) and image collectors that collect the returned energy (echo)to create an intravascular image. The imaging transducers and imagingcollectors are coupled to signal lines that run through the length ofthe catheter and couple to the computerized ultrasound equipment.

IVUS imaging assemblies produce ultrasound energy and receive echoesfrom which real time ultrasound images of a thin section of the bloodvessel are produced. The imaging transducers of the imaging element areconstructed from piezoelectric components that produce sound energy at20-50 MHz. The image collectors of the imaging element comprise separatepiezoelectric elements that receive the ultrasound energy that isreflected from the vasculature. Alternative embodiments of imagingassembly may use the same piezoelectric components to produce andreceive the ultrasonic energy, for example, by using pulsed ultrasound.That is, the imaging transducer and the imaging collectors are the same.Another alternative embodiment may incorporate ultrasound absorbingmaterials and ultrasound lenses to increase signal to noise.

IVUS data is typically gathered in segments where each segmentrepresents an angular portion of an IVUS image. Thus, it takes aplurality of segments (or a set of IVUS data) to image an entirecross-section of a vascular object. Furthermore, multiple sets of IVUSdata are typically gathered from multiple locations within a vascularobject (e.g., by moving the transducer linearly through the vessel).These multiple sets of data can then be used to create a plurality oftwo-dimensional (2D) images or one three-dimensional (3D) image.

IVUS imaging assemblies and processing of IVUS data are described infurther detail in, for example, Yock, U.S. Pat. Nos. 4,794,931,5,000,185, and 5,313,949; Sieben et al., U.S. Pat. Nos. 5,243,988, and5,353,798; Crowley et al., U.S. Pat. No. 4,951,677; Pomeranz, U.S. Pat.No. 5,095,911, Griffith et al., U.S. Pat. No. 4,841,977, Maroney et al.,U.S. Pat. No. 5,373,849, Born et al., U.S. Pat. No. 5,176,141, Lancee etal., U.S. Pat. No. 5,240,003, Lancee et al., U.S. Pat. No. 5,375,602,Gardineer et at., U.S. Pat. No. 5,373,845, Seward et al., Mayo ClinicProceedings 71(7):629-635 (1996), Packer et al., Cardiostim Conference833 (1994), “Ultrasound Cardioscopy,” Eur. J.C.P.E. 4(2):193 (June1994), Eberle et al., U.S. Pat. No. 5,453,575, Eberle et al., U.S. Pat.No. 5,368,037, Eberle et at., U.S. Pat. No. 5,183,048, Eberle et al.,U.S. Pat. No. 5,167,233, Eberle et at., U.S. Pat. No. 4,917,097, Eberleet at., U.S. Pat. No. 5,135,486, U.S. Pub. 2009/0284332; U.S. Pub.2009/0195514 A1; U.S. Pub. 2007/0232933; and U.S. Pub. 2005/0249391 andother references well known in the art relating to intraluminalultrasound devices and modalities.

OCT is a medical imaging methodology using a miniaturized near infraredlight-emitting probe. As an optical signal acquisition and processingmethod, it captures micrometer-resolution, three-dimensional images fromwithin optical scattering media (e.g., biological tissue). Recently ithas also begun to be used in interventional cardiology to help diagnosecoronary artery disease. OCT allows the application of interferometrictechnology to see from inside, for example, blood vessels, visualizingthe endothelium (inner wall) of blood vessels in living individuals.

OCT systems and methods are generally described in Castella et al., U.S.Pat. No. 8,108,030, Milner et al., U.S. Patent Application PublicationNo. 2011/0152771, Condit et al., U.S. Patent Application Publication No.2010/0220334, Castella et al., U.S. Patent Application Publication No.2009/0043191, Milner et al., U.S. Patent Application Publication No.2008/0291463, and Kemp, N., U.S. Patent Application Publication No.2008/0180683, the content of each of which is incorporated by referencein its entirety.

In OCT, a light source delivers a beam of light to an imaging device toimage tar tissue. Light sources can include pulsating light sources orlasers, continuous wave light sources or lasers, tunable lasers,broadband light source, or multiple tunable laser. Within the lightsource is an optical amplifier and a tunable filter that allows a userto select a wavelength of light to be amplified. Wavelengths commonlyused in medical applications include near-infrared light, for examplebetween about 800 nm and about 1700 nm.

Aspects of the invention may obtain imaging data from an OCT system,including OCT systems that operate in either the time domain orfrequency (high definition) domain. Basic differences betweentime-domain OCT and frequency-domain OCT is that in time-domain OCT, thescanning mechanism is a movable mirror, which is scanned as a functionof time during the image acquisition. However, in the frequency-domainOCT, there are no moving parts and the image is scanned as a function offrequency or wavelength.

In time-domain OCT systems an interference spectrum is obtained bymoving the scanning mechanism, such as a reference mirror,longitudinally to change the reference path and match multiple opticalpaths due to reflections within the sample. The signal giving thereflectivity is sampled over time, and light traveling at a specificdistance creates interference in the detector. Moving the scanningmechanism laterally (or rotationally) across the sample producestwo-dimensional and three-dimensional images. In frequency domain OCT, alight source capable of emitting a range of optical frequencies excitesan interferometer, the interferometer combines the light returned from asample with a reference beam of light from the same source, and theintensity of the combined light is recorded as a function of opticalfrequency to form an interference spectrum. A Fourier transform of theinterference spectrum provides the reflectance distribution along thedepth within the sample.

Several methods of frequency domain OCT are described in the literature.In spectral-domain OCT (SD-OCT), also sometimes called “Spectral Radar”(Optics letters, Vol. 21, No. 14 (1996) 1087-1089), a grating or prismor other means is used to disperse the output of the interferometer intoits optical frequency components. The intensities of these separatedcomponents are measured using an array of optical detectors, eachdetector receiving an optical frequency or a fractional range of opticalfrequencies. The set of measurements from these optical detectors formsan interference spectrum (Smith, L. M. and C. C. Dobson, Applied Optics28: 3339-3342), wherein the distance to a scatterer is determined by thewavelength dependent fringe spacing within the power spectrum. SD-OCThas enabled the determination of distance and scattering intensity ofmultiple scatters lying along the illumination axis by analyzing asingle the exposure of an array of optical detectors so that no scanningin depth is necessary. Typically the light source emits a broad range ofoptical frequencies simultaneously.

Alternatively, in swept-source OCT, the interference spectrum isrecorded by using a source with adjustable optical frequency, with theoptical frequency of the source swept through a rang of opticalfrequencies, and recording the interfered light intensity as a functionof time during the sweep. An example of swept-source OCT is described inU.S. Pat. No. 5,321,501.

Generally, time domain systems and frequency domain systems can furthervary in type based upon the optical layout of the systems: common beampath systems and differential beam path systems. A common beam pathsystem sends all produced light through a single optical fiber togenerate a reference signal and a sample signal whereas a differentialbeam path system splits the produced light such that a portion of thelight is directed to the sample and the other portion is directed to areference surface. Common beam path systems are described in U.S. Pat.No. 7,999,938; U.S. Pat. No. 7,995,210; and U.S. Pat. No. 7,787,127 anddifferential beam path systems are described in U.S. Pat. No. 7,783,337;U.S. Pat. No. 6,134,003; and U.S. Pat. No. 6,421,164, the contents ofeach of which are incorporated by reference herein in its entirety.

According to certain aspects of the invention, the obtained image datafrom the imaging assembly of the atherectomy systems described herein isprocessed to characterize biological material and/or foreign material(i.e. the occlusion) within the vessels. The characterization allows oneto determine with specificity the type of occlusion within the vessel(e.g. plaque or clot) and the severity of the occlusion, e.g., whetherthe occlusion is calcified, fibrous, or soft. The processing step may beperformed by an image processing computer operably connected to theimaging assembly via signal wires.

Referring now to FIG. 16, the atherectomy system 10 may be coupled toand coordinated by a system controller 600. The system controller 1600may control the timing, duration, and amount of imaging. Accordingly tocertain embodiments, the system controller 1600 may also control therotation of the torque shaft (and cutting elements coupled thereto) andmay also rotation of the catheter body (and imaging assemblies andhousing coupled thereto). As shown in FIG. 17, the system controller1600 is additionally interfaced with image processing computer 1060.According to certain embodiments, the processor 1065 of the imageprocessing computer 1060 performs tissue/blood characterization, therebyallowing the viewed and assessed images to be the basis for definingparameters for complete treatment and dissolution of the blockage. Thesystem 1000 also includes a display 1620 and a user interface that allowa user, e.g. a surgeon, to interact with the images (including tissuecharacterization) and to control the parameters of the treatment.

As shown in FIG. 16, a system controller 1600 is interfaced to an imageprocessing computer 1060 that is capable of synthesizing the images intoeasy-to-understand images. The image processing computer 1060 is alsoconfigured to analyze the spectrum of the collected data to determinetissue characteristics, a.k.a. virtual histology. As discussed ingreater detail below, the image processing will deconvolve the reflectedacoustic waves or interfered infrared waves to produce distance and/ortissue measurements, and those distance and tissue measurements can beused to produce an image, for example an IVUS image or an OCT image.Flow detection and tissue characterization algorithms, includingmotion-detection algorithms (such as CHROMAFLO (IVUS fluid flow displaysoftware; Volcano Corporation), Q-Flow, B-Flow, Delta-Phase, Doppler,Power Doppler, etc.), temporal algorithms, harmonic signal processing,can be used to differentiate blood speckle from other structural tissue,and therefore enhance images where ultrasound energy back scattered fromblood causes image artifacts.

In certain embodiments, the image processing may additionally includespectral analysis, i.e., examining the energy of the returned acousticsignal at various frequencies. Spectral analysis is useful fordetermining the nature of the tissue and the presence of foreignobjects. A plaque deposit or neointimal hyperplasia, for example, willtypically have different spectral signatures than nearby vascular tissuewithout such plaque or neointimal hyperplasia, allowing discriminationbetween healthy and diseased tissue. Also a metal surface, such as a AVgraft, will have a different spectral signal. Such signal processing mayadditionally include statistical processing e.g., averaging, filtering,or the like) of the returned ultrasound signal in the time domain. Thespectral analysis can also be used to determine the tissue lumen/bloodborder. Other signal processing techniques known in the art of tissuecharacterization may also be applied. By distinguishing the between theabove referenced features within the vessel, one is able to carefullydissolve the blockage without disrupting the surrounding vessel tissue.

Other image processing may facilitate use of the images oridentification of features of interest. For example, the border of alumen may be highlighted or thrombus or plaque deposits may be displayedin a visually different manner by assigning thrombus a discerniblecolor) than other portions of the image. Other image enhancementtechniques known in the art of imaging may also be applied. In a furtherexample, similar techniques can be used to discriminate betweenvulnerable plaque and other plaque, or to enhance the displayed image byproviding visual indicators to assist the user in discriminating betweenvulnerable and other plaque. Other measurements, such as flow rates orpressure may be displayed using color mapping or by displaying numericalvalues. In some embodiments, the open cross-sectional area of the lumenis colorized with red to represent the blood flux. Thus, by usingvirtual histology (spectral analysis), methods of the invention allowone to assess the blockage before, during, and after treatment.

In addition to the above disclosed systems, the following systems fordetecting and characterizing plaque and biological tissue using virtualhistology are disclosed in U.S. Pat. No. 6,200,268 entitled “VASCULARPLAQUE CHARACTERIZATION” issued Mar. 13, 2001, U.S. Pat. No. 6,381,350entitled “INTRAVASCULAR ULTRASONIC ANALYSIS USING ACTIVE CONTOUR METHODAND SYSTEM” issued Apr. 30, 2002, U.S. Pat. No. 7,074,188 entitled“SYSTEM AND METHOD OF CHARACTERIZING VASCULAR TISSUE” issued Jul. 11,2006, U.S. Pat. No. 7,175,597 entitled “NON-INVASIVE TISSUECHARACTERIZATION SYSTEM AND METHOD” issued Feb. 13, 2007, U.S. Pat. No.7,215,802 entitled “SYSTEM AND METHOD FOR VASCULAR BORDER DETECTION”issued May 8, 2007, U.S. Pat. No. 7,359,554 entitled “SYSTEM AND METHODFOR IDENTIFYING A VASCULAR BORDER” issued Apr. 15, 2008, and U.S. Pat.No. 7,463,759 entitled “SYSTEM AND METHOD FOR VASCULAR BORDER DETECTION”issued Dec. 9, 2008.

INCORPORATION BY REFERENCE

References and citations to other documents, such as patents, patentapplications, patent publications, journals, books, papers, webcontents, have been made throughout this disclosure. All such documentsare hereby incorporated herein by reference in their entirety for allpurposes.

EQUIVALENTS

Various modifications of the invention and many further embodimentsthereof, in addition to those shown and described herein, will becomeapparent to those skilled in the art from the full contents of thisdocument, including references to the scientific and patent literaturecited herein. The subject matter herein contains important information,exemplification and guidance that can be adapted to the practice of thisinvention in its various embodiments and equivalents thereof.

What is claimed is:
 1. An apparatus for cutting and removing occlusivematerial, the apparatus comprising: a catheter body defining a firstlumen and comprising a distal housing that defines an opening; arotatable shaft disposed within the first lumen of the catheter body,wherein the rotatable shaft comprises a conveying component and acutting element that is at least partially surrounded by the distalhousing; and an imaging element located on the distal housing.
 2. Theapparatus of claim 1, wherein the imaging element circumscribes thedistal housing.
 3. The apparatus of claim 2, wherein the imaging elementcomprises an ultrasound transducer.
 4. The apparatus of claim 3, whereinthe ultrasound transducer is a phased-array transducer.
 5. The apparatusof claim 3, wherein the ultrasound transducer is configured to image ina plane distal to the ultrasound transducer.
 6. The apparatus of claim1, wherein the apparatus further comprises at least one other cuttingelement.
 7. The apparatus of claim 1, wherein the cutting elementcomprise at least two helical flutes.
 8. The apparatus of claim 1,wherein the cutting element comprises at least one crushing element. 9.The apparatus of claim 8, wherein the crushing element is substantiallyrectangular and comprises a negative rake angle.
 10. The apparatus ofclaim 1, wherein the catheter body and the housing are configured torotate.
 11. The apparatus of claim 10, wherein the catheter body and thehousing rotate in the opposite direction of the rotatable shaft.
 12. Theapparatus of claim 1, further comprising a discharge element operablyassociated with the catheter body, the discharge element configured toreceive occlusive material morcellated by the cutting element.
 13. Theapparatus of claim 1, wherein the conveying component comprises ahelical wire wound about the rotatable shaft.
 14. The apparatus of claim13, wherein the helical wire has a substantially rectangularcross-section.
 15. An apparatus for cutting and removing occlusivematerial, the apparatus comprising: a catheter body defining a firstlumen and comprising a distal end; a rotatable shaft disposed within thefirst lumen of the catheter body and comprising a conveying componentalong the length of the rotatable shaft; a cutting element operablycoupled to the rotatable shaft; and a housing coupled to the distal endof the catheter body, the housing defines a distal opening, at leastpartially surrounds the cutting member, and comprises an imagingelement.
 16. The apparatus of claim 15, wherein the imaging elementcircumscribes the distal housing.
 17. The apparatus of claim 16, whereinthe imaging element comprises an ultrasound transducer.
 18. Theapparatus of claim 17, wherein the ultrasound transducer is configuredto image in a plane distal to the ultrasound transducer.
 19. Theapparatus of claim 15, wherein the cutting element comprise at least twohelical flutes.
 20. The apparatus of claim 15, wherein the cuttingelement comprises at least one crushing element.
 21. The apparatus ofclaim 20, wherein the crushing element is substantially rectangular andcomprises a negative rake angle.
 22. The apparatus of claim 15, whereinthe catheter body and the housing are configured to rotate.
 23. Theapparatus of claim 22, wherein the catheter body and the housing rotatein the opposite direction of the rotatable shaft.
 24. The apparatus ofclaim 15, wherein the conveying component comprises a helical wire woundabout the rotatable shaft.
 25. The apparatus of claim 24, wherein thehelical wire has a substantially rectangular cross-section.
 26. Anapparatus for cutting and removing occlusive material, the apparatuscomprising: a catheter body defining a first lumen and comprising adistal end; a rotatable shaft disposed within the first lumen of thecatheter body and comprising a conveying component along the length ofthe rotatable shaft; a cutting element operably coupled to the rotatableshaft, wherein the cutting element comprises at least one blade elementwith a positive rake angle and at least one crushing element with anegative rake angle; and a housing coupled to the distal end of thecatheter body, the housing defining a distal opening and at leastpartially surrounding the cutting member.